A replicated, randomized, controlled study in 1993–1997 in a rainfed barley field near Madrid, Spain, found higher barley yields in plots with vetch-barley or fallow-barley rotations, compared to plots with continuous barley. Crop yield: Higher barley yields were found in plots with rotations (4,107–4,395 vs 2,465 kg/ha). Methods: Barley was grown continuously (one plot), or in rotation with vetch Vicia sativa or fallow (one plot/phase), in each of three tillage treatments (conventional, reduced, or no tillage), in each of four blocks. Plots were 10 x 25 m. The barley phases were fertilized (8-24-8 NPK: 200 kg/ha; ammonium nitrate: 200 kg/ha). Before the experiment, barley was grown in these plots for over 10 years. Barley was harvested in June.

A replicated, randomized, controlled study in 1993–2000 in arable farmland in Madrid, Spain, found less phosphorus in plots with fallow-barley rotations, compared to continuous barley. Organic matter: Similar amounts of organic carbon were found in soils with or without crop rotations (data not reported). Nutrients: Less phosphorus was found in soils with crop rotations, compared to continuous barley, in one of six comparisons (compared to fallow-barley at one depth: 16 vs 18 kg/ha). Similar amounts of nitrogen, and similar pH levels, were found in soils with or without rotations (0.9–1.8 Mg/ha; data not reported for pH). Methods: Barley was grown continuously (one plot), or in rotation with vetch Vicia sativa or fallow (one plot/phase), in each of three tillage treatments (conventional, reduced, or no tillage), in each of four blocks. Plots were 10 x 25 m. The barley phases were fertilized (8-24-8 NPK: 200 kg/ha; ammonium nitrate: 200 kg/ha). Before the experiment, barley was grown in these plots for over 10 years. Barley was harvested in June. Soil samples were collected after each harvest (0–90 cm depth).

A replicated, randomized, controlled study in 1993–1997 in a rainfed barley field near Madrid, Spain, found lower crop yields in plots with no tillage, compared to conventional tillage. Crop yield: Lower barley yields were found in plots with no tillage, compared to conventional tillage (1995–1997: 3,593 vs 4,312 kg/ha). Methods: No tillage or conventional tillage was used on four plots each (five 10 x 25 m subplots/plot, with barley monocultures or barley rotations). A mouldboard plough (30 cm depth) and a cultivator (10–15 cm depth, when needed for weed control) were used for conventional tillage. Pre-emergence herbicide was used for no tillage. The barley was fertilized (NPK: 200 kg/ha; ammonium nitrate: 200 kg/ha).

A replicated, randomized, controlled study in 1993-2000 in a rainfed field near Madrid, Spain, found lower crop yields in plots with reduced tillage, compared to conventional tillage. Crop yield: Lower barley yields were found in plots with reduced tillage, compared to conventional tillage (3,061 vs 4,312 kg/ha). Methods: Conventional tillage or reduced tillage was used on 20 subplots each (10 x 25 m subplots). Barley-barley, barley-vetch, or barley-fallow rotations were used on the subplots. A mouldboard plough (30 cm depth) was used for conventional tillage. A chisel plough (20 cm depth) was used for reduced tillage. Barley was fertilized, but vetch and fallows were not. Herbicide was used when needed. Barley was sown in October and harvested in June. Soil samples were collected after harvest (0–90 cm depth; nitrogen was measured at 0–30 cm depth; phosphorus and potassium at 0–80 cm depth).

A replicated, randomized, controlled study in 1993–1997 in a rainfed barley field near Madrid, Spain (same study as (19,37,39)), found more organic matter, phosphorus, and potassium in soils with no tillage, compared to conventional tillage, but tillage had inconsistent effects on nitrogen. Organic matter: More organic carbon was found in soils with no tillage, compared to conventional tillage, in six of eight comparisons (8–11 vs 4–6 Mg/ha), but less was found in one of eight comparisons (6 vs 7 Mg/ha). Nutrients: More nitrogen was found in soils with no tillage, compared to conventional tillage, in six of eight comparisons (0.7–1.4 vs 0.4–0.9 Mg total N/ha), but less was found in one of eight comparisons (0.5 vs 0.6 Mg/ha). More potassium and phosphorus were found in soils with no tillage, compared to conventional tillage, in two of four comparisons (in 1997: 13–17 vs 7–8 kg extractable P/ha; 250–310 vs 150–190 kg extractable K/ha). Similar pH was found in soils with no tillage or conventional tillage (pH 7.8). Methods: No tillage or conventional tillage was used on four plots each (five 10 x 25 m subplots/plot, with barley monocultures or barley rotations). A mouldboard plough (30 cm depth) and a cultivator (10–15 cm depth, when needed for weed control) were used for conventional tillage. Pre-emergence herbicide was used for no tillage. The barley was fertilized (NPK: 200 kg/ha; ammonium nitrate: 200 kg/ha). Soil samples were collected after the harvest in 1994–1997 (0–90 cm depth; organic matter and nitrogen were assessed at 0–30 cm depth).

A replicated, randomized, controlled study in 1993–2000 in a rainfed field near Madrid, Spain, found more phosphorus and potassium in soils with reduced tillage, compared to conventional tillage, but tillage had inconsistent effects on nitrogen. Nutrients: More nitrogen was found in soils with reduced tillage, compared to conventional tillage, in six of eight comparisons (0.7–1.3 vs 0.4–0.9 mg/ha), but less was found in one of eight comparisons (0.5 vs 0.6 mg/ha). More phosphorus was found in soils with reduced tillage, compared to conventional tillage, in two of four comparisons in 1997 (12–13 vs 7–8 kg/ha). More potassiumwas found in soils with reduced tillage, compared to conventional tillage, in two of four comparisons in 1997 (230–260 vs 150–190 kg/ha). Similar pH was found in soils with reduced tillage or conventional tillage (pH 7.8). Methods: Conventional tillage or reduced tillage was used on 20 subplots each (10 x 25 m subplots). Barley-barley, barley-vetch, or barley-fallow rotations were used on the subplots. A mouldboard plough (30 cm depth) was used for conventional tillage. A chisel plough (20 cm depth) was used for reduced tillage. Barley was fertilized, but vetch and fallows were not. Herbicide was used when needed. Soil samples were collected after harvest (0–90 cm depth; nitrogen was measured at 0–30 cm depth; phosphorus and potassium at 0–80 cm depth).